Whether it was a 100-carat diamond, a miniature Old Master painting or a custom-painted Porsche owned by a legendary rock star, Sotheby's witnessed some true treasures in 2015. With sales all around the globe, Sotheby’s Instagram is where our international happenings are united. Commemorating our thrilling year, here are 25 of our most popular and dynamic Instagram shots following works into our buildings, on display and under the hammer.